Dryer appliances generally include a cabinet with a drum rotatably mounted therein. During operation, a motor rotates the drum, e.g., to tumble articles located within a chamber defined by the drum. Dryer appliances also generally include a heater assembly that passes heated air through the chamber in order to dry moisture-laden articles positioned therein. Typically, an air handler or blower is used to urge the flow of heated air from chamber, through a trap duct, and to the exhaust duct where it is exhausted from the dryer appliance. Dryer appliances may further include filter systems for removing foreign materials, such as lint, from passing into the exhaust conduit, which can impair dryer performance and may present a fire hazard due to the potential for combustion.
Conventional heater assemblies include electrical resistance heaters such as wire coils that generate heat when electrical current is passed through them. Notably, these resistance heaters are typically only 70-80% efficient, resulting in significant wasted energy during operation. In addition, for example, current dryer appliances include two resistance heater coils which are connected to three-phase power systems to energize these heaters in one of three steps—OFF for no heat, one heater ON for low heat, or two heaters ON for high heat. Therefore, the temperature within the drum may not be controlled linearly, resulting in significant operating restrictions and limited versatility in terms of using different operating cycles to dry various load types.
Accordingly, improved dryer appliances including features for improved heating versatility are desirable. More specifically, dryer appliances including features for efficiently and linearly controlling a drum temperature would be particularly beneficial.